The human heart can suffer from various valvular diseases. These valvular diseases can result in significant malfunctioning of the heart and ultimately require repair of the native valve or replacement of the native valve with an artificial valve. There are a number of known repair devices (e.g., stents) and artificial valves, as well as a number of known methods of implanting these devices and valves in humans. Because of the drawbacks associated with conventional open-heart surgery, percutaneous and minimally-invasive surgical approaches are garnering intense attention. In one technique, a prosthetic device is configured to be implanted in a much less invasive procedure by way of catheterization. For example, collapsible transcatheter prosthetic heart valves can be crimped to a compressed state and percutaneously introduced in the compressed state on a catheter and expanded to a functional size at the desired position by balloon inflation or by utilization of a self-expanding frame or stent.
A challenge of implanting a self-expanding prosthetic valve via a catheterization is control of the expansion of the prosthetic valve as the prosthetic valve is deployed from a distal end of a delivery apparatus (i.e., the end of the apparatus that is advanced into a patient's heart) during the implantation procedure. Typically, a self-expanding prosthetic valve expands rapidly when it is exposed from a delivery cylinder or sheath. The rapid expansion can cause the prosthetic valve to migrate or “jump” from a desired deployment position within the patient's heart. As such, the prosthetic valve must subsequently be repositioned to the desired deployment position.
Another challenge of self-expandable prosthetic valves includes repositioning and/or retrieving the prosthetic valve once it is expanded to the functional size. Repositioning the prosthetic valve can be relatively more difficult in the expanded, functional state because the increased radial profile of the prosthetic valve can cause the prosthetic valve to engage the native anatomy (e.g., the native annulus) of the patient's heart, which can interfere or prevent the prosthetic valve from moving freely within the patient's heart. Retrieving the prosthetic valve can be relatively more difficult once the prosthetic valve is expanded because it can be difficult to exert sufficient radial force on the prosthetic valve to cause it to radially compress so that it can be retracted into a delivery cylinder.
An additional challenge is that about fifty percent of self-expanding prosthetic valves require a balloon post-dilation procedure to expand the prosthetic valve to its nominal diameter and/or to reduce paravalvular leakage. This additional procedure can add undesirable steps and thus time to an implantation procedure.
Thus, there is a continuing need for improved transcatheter prosthetic devices and delivery apparatuses for implanting such devices.